Decorating material

ABSTRACT

There is provided a decorative material which hardly undergoes deterioration of a substrate even when irradiated with an electron beam, and is excellent in surface properties such as stain resistance, abrasion resistance and marring resistance. The decorative material of the present invention includes a substrate, and a pattern layer and/or a colored layer, and a surface protective layer which are successively laminated on the substrate, wherein the surface protective layer is obtained by crosslinking and curing an electron beam-curable resin composition, and a rate of reduction in a folding endurance of a material obtained by applying the electron beam-curable resin composition onto the substrate and then irradiating an electron beam to the electron beam-curable resin composition, relative to a folding endurance of the substrate before applying the electron beam-curable resin composition thereonto is 70% or lower as measured in the CD direction (lateral direction) of the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of application Ser. No. 11/337,069 filed Jan. 23,2006, which claims priority from Japanese Patent Application No.2005-015414 filed Jan. 24, 2005; the above noted prior applications areall hereby incorporated by reference.

FIELD OF INVENTION

The present invention relates to decorative materials having a surfaceprotective layer obtained by crosslinking and curing an electronbeam-curable resin composition which hardly suffer from deterioration ofa substrate due to exposure to electron beam and are excellent insurface properties such as stain resistance, abrasion resistance andmarring resistance.

BACKGROUND OF INVENTION

Decorative materials used in the applications including buildinginterior materials such as walls, fittings for buildings such as doors,surface materials for furniture, etc., have been usually required toexhibit good surface properties such as abrasion resistance and stainresistance. Hitherto, there has been proposed the decorative sheethaving a surface resin layer which is produced, for example, by forminga pattern layer on a substrate made of papers or plastics by a printingmethod, applying an ionizing radiation-curable resin coating material onthe substrate to form a coating resin layer, and then irradiating anelectron beam to the coating resin layer for crosslinking and curing theresin composition to form the surface resin layer (for example, refer toJapanese Patent Publication No. 31033/1974). When such a surface resinlayer obtained by irradiating an ionizing radiation such as an electronbeam to the applied ionizing radiation-curable resin made of monomers,prepolymers, etc., to crosslink and cure the resin is provided as anoutermost layer of a decorative sheet, the resultant decorative sheet isexcellent in abrasion resistance, stain resistance, etc., due to a highcrosslinkability thereof.

However, when irradiating the ionizing radiation for crosslinking thesurface resin layer, the conventional decorative materials, for example,those using a substrate made of papers, tend to suffer from cutting orbreaking of cellulose molecules of pulps in the paper substrate tothereby generate a carboxyl group or a carbonyl group at a cut or brokenend of the molecules. As a result, the paper substrate tends to bedeteriorated in strength, resulting in deteriorated processability ofthe decorative material. Whereas, a plastic substrate also tends tosuffer from cutting or breaking of polymer molecular chains uponirradiation of the ionizing radiation, resulting in deterioration instrength thereof. For these reasons, when the decorative sheet islaminated under pressure on the substrate as an adherend such as plywoodthrough an adhesive, the decorative sheet tends to undergo increasedtension, resulting in occurrence of split therein due to mechanicalvibration, etc.

In particular, when the decorative sheet is laminated on curved portionsof the adherend substrate or corner edge portions of such an adherendsubstrate having a polyhedral column shape by a wrapping process, thedecorative sheet tends to suffer from concentrated local stress,resulting in breakage of the decorative sheet. The wrapping method isexplained in detail by referring to the conceptual view shown in FIG. 2.

As shown in FIG. 2, a column-shaped substrate B is placed on a transportapparatus 10, and transported in a length direction thereof [MDdirection (longitudinal direction: machine direction) of the substrate,i.e., the direction shown by an outlined arrow in FIG. 2]. A wrappingdecorative sheet S is fed onto the column-shaped substrate B at a speedsynchronized with a transporting speed of the substrate, and laminatedon plural aide surfaces of the column-shaped substrate by means of aplurality of pressing rollers Ra to Re which are arranged in differentdirections from each other. The lamination of the wrapping decorativesheet S is stepwise conducted every small area portion thereof in thedirection substantially perpendicular or just perpendicular to thelongitudinal direction of the column-shaped substrate (CD direction:cross machine direction). The wrapping decorative sheet S is firstlaminated on a central portion of a side surface of the column-shapedsubstrate in the width direction thereof by means of the pressing rollerRa, and then successively laminated on adjacent portions of the sidesurface of the column-shaped substrate by means of the pressing rollersRb and Rc and further on outer adjacent portions of the side surface ofthe column-shaped substrate by means of the pressing rollers Rd and Reto cover the desired side surface of the column-shaped substrate withthe wrapping decorative sheet. Upon such a wrapping process, since thewrapping decorative sheet is pressed by the pressing rollers Ra to Reunder tension applied in the CD direction, the to strength thereof inparticular, in the CD direction, is important.

On the other hand, for the purpose of improving a processability of sucha decorative material having a surface protective layer obtained bycrosslinking and curing an ionizing radiation-curable resin, there hasbeen proposed the decorative material composed of a surface resin layermade of a crosslinked product of the ionizing radiation-curable resin, apaper substrate and a high-modulus resin layer having a specific tensilestrength which are laminated on each other from its front-side surfacetoward its backside surface in this order (refer to claims of JapanesePatent Application Laid-open No. 14490/2002).

Thus, when the high-modulus resin layer is provided on the backsidesurface of the paper substrate, even though cellulose molecules of pulpsof the paper substrate is cut or broken owing to irradiation with theionizing radiation to thereby cause deterioration in strength of thepaper substrate, the deteriorated strength of the paper substrate can becompensated with the high-modulus resin layer on the backside surface,so that the decorative sheet can maintain a suitable strength as awhole. As a result, the resultant decorative sheet can exhibit not onlygood surface properties such as abrasion resistance owing to theprovision of the surface protective layer but also good processability.

However, the above conventional method requires formation of thehigh-modulus resin layer, resulting in various limitations to productionof the decorative materials. Therefore, it has been demanded to providethe method of suppressing deterioration of the substrate itself.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the above conventionalproblems. An object of the present invention is to provide a decorativematerial which hardly undergoes deterioration of the substrate even whenirradiated with an electron beam, and is excellent in surface propertiessuch as stain resistance and abrasion resistance.

As a result of intensive and extensive researches to achieve the aboveobject, the inventors have found that when an acceleration voltage andan exposure dose of electron beam applied is well controlled accordingto kind of the substrate, more specifically, when a rate of reduction ina folding endurance of a material obtained by applying an electronbeam-curable resin composition onto the substrate and then irradiatingan electron beam thereto, relative to a folding endurance of thesubstrate before applying the electron beam-curable resin compositionthereonto is controlled to 70% or lower as measured in the CD direction(lateral direction) of the substrate, the resultant decorative materialhardly undergoes deterioration of the substrate even when irradiatedwith an electron beam, and can exhibit excellent surface properties suchas stain resistance, abrasion resistance and marring resistance. Thepresent invention has been accomplished on the basis of the finding.

Thus, the present invention provides:

(1) A decorative material comprising a substrate, and a pattern layerand/or a colored layer, and a surface protective layer which aresuccessively laminated on the substrate, wherein the surface protectivelayer is obtained by crosslinking and curing an electron beam-curableresin composition, and a rate of reduction in a folding endurance of amaterial obtained by applying the electron beam-curable resincomposition onto the substrate and then irradiating an electron beam tothe electron beam-curable resin composition, relative to a foldingendurance of the substrate before applying the electron beam-curableresin composition thereonto is 70% or lower as measured in the CDdirection (lateral direction) of the substrate;

(2) the decorative material as described in the above aspect (1),wherein the electron beam is irradiated to the electron beam-curableresin composition at an acceleration voltage of 30 to 150 kV and anexposure dose of 30 to 70 kGy.

(3) the decorative material as described in the above aspect (1) or (2),wherein the substrate is a fibrous substrate;

(4) the decorative material as described in the above aspect (3),wherein the substrate is a cellulose-based substrate;

(5) A decorative plate comprising a substrate and the decorativematerial as described in any one of the above aspects (1) to (4) whichis laminated on the substrate; and

(6) a process for producing a decorative material comprising asubstrate, and a pattern layer and/or a colored layer, and a surfaceprotective layer which are successively laminated on the substrate,wherein the surface protective layer is obtained by crosslinking andcuring an electron beam-curable resin composition, and the electron beamis irradiated to the electron beam-curable resin composition at anacceleration voltage of 30 to 150 kV and an exposure dose of 30 to 70kGy.

Effect of the Invention

In accordance with the present invention, there is provided a decorativematerial which hardly suffers from deterioration of a substrate evenwhen irradiated with an electron beam and is excellent surfaceproperties such as stain resistance, abrasion resistance and marringresistance. More specifically, since the substrate is hardlydeteriorated even when irradiated with an electron beam, the resultantdecorative material can be improved in processability and, therefore,can follow even a complicated shape upon wrapping thereon. Further, thedecorative material is free from breakage, for example, even whenprocessed in the winter, i.e., under a low-temperature and dryatmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a section of a decorative materialaccording to the present invention.

FIG. 2 is a conceptual view showing a wrapping process.

FIG. 3 is a schematic view showing a section of a decorative materialaccording to the present invention, in which the decorative material hasa second substrate (represented in the figure by the term “2ndsubstrate”).

EXPLANATION OF REFERENCE NUMERALS

-   -   1: Decorative material; 2: Substrate; 3: Colored layer; 4:        Pattern layer; 5: Penetration-preventing layer; 6: Surface        protective layer; 10: Transport apparatus; B: Column-shaped        substrate; S: Wrapping decorative sheet; Ra to Re: Pressing        rollers

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

The decorative material of the present invention includes a substrate, apattern layer and/or a colored layer formed on the substrate, and asurface protective layer which is formed on the pattern layer and/orcolored layer either directly or through the other layer(s) by applyingan electron beam-curable resin composition and irradiating an electronbeam thereto for crosslinking and curing the resin composition. Thedecorative material of the present invention is characterized in that arate of reduction in a folding endurance of the decorative materialobtained after applying the electron beam-curable resin composition andirradiating an electron beam to the resin composition for crosslinkingand curing thereof (hereinafter referred to as an “electronbeam-irradiated decorative material”) as measured in the CD direction(lateral direction) of the substrate, relative to a folding endurance ofthe decorative material before applying the electron beam-curable resincomposition (hereinafter referred to merely as “dry paper”) as measuredin the same CD direction is 70% or lower. The folding endurance usedherein means the number of folding reciprocating motions required untilreaching breakage of a test specimen of the decorative material asmeasured according to TAPPI T511 [Folding Endurance of Paper (MITTesting Machine)].

The typical structure of the decorative material according to thepresent invention is explained by referring to FIG. 1 which is aschematic view showing a section of a decorative material 1 of thepresent invention. In the embodiment shown in FIG. 1, a colored layer 3uniformly covering a whole surface of a substrate 2, a pattern layer 4,a uniform penetration-preventing layer 5 and a surface protective layer6 obtained by crosslinking and curing an electron beam-curable resincomposition are successively laminated on the substrate 2 in this order.

In order to control the rate of reduction in folding endurance of theelectron beam-irradiated decorative material relative to a foldingendurance of the dry paper to 70% or lower, although various factors areconsidered, it is important to suitably select the respectiveconstituents of the decorative material and control the intensity andexposure dose of an electron beam irradiated for crosslinking and curingthe surface protective layer 6. In the followings, the respectiveconstituents as well as the intensity and exposure dose of the electronbeam irradiated are explained in detail.

The substrate 2 used in the present invention is not particularlylimited as long as it is ordinarily usable for decorative materials, andmay be appropriately selected from fibrous substrates such as variouspapers, plastic films, plastic sheets, metal foils, metal sheets, metalplates, wood plates such as timber, and ceramic-based materialsaccording to the applications thereof. In the present invention, amongthese substrates, the fibrous substrates may be especially effectivelyused.

These materials may be used alone or in the form of a laminate composedof an optional combination thereof such as a composite of papers and acomposite of a paper and a plastic film. One or both surfaces of thesubstrate, in particular, a plastic film substrate or a plastic sheetsubstrate, may be subjected to physical or chemical surface treatmentssuch as those using an oxidation method or a convex/concave formingmethod, if required, in order to enhance adhesion of the substrate tothe layer to be laminated thereon.

Examples of the treatments using the oxidation method include a coronadischarge treatment, a chromate treatment, a flame treatment, a hot airtreatment and an ozone/ultraviolet treatment. Examples of the treatmentsusing the convex/concave forming method include a sand blast treatmentand a solvent treatment. These surface treatments may be appropriatelyselectively conducted depending upon the kind of substrate used. Ingeneral, among these treatments, the corona discharge treatment ispreferably used in view of good effects and facilitated operationthereof.

In addition, the substrate may also be treated to form a primer layerthereon. Further, the substrate may be coated with a suitable paint toadjust a hue thereof or may be previously formed thereon with a patternin view of imparting a good design thereto.

Examples of various papers used as the substrate include thin cut sheetpapers, kraft papers and titanium papers. These paper substrates mayfurther contain resins such as acrylic resins, styrene-butadienerubbers, melamine resins and urethane resins in order to enhance aninterlaminar bonding strength between fibers of the paper substrate orbetween the paper substrate and the other layers, or prevent formationof fuzzes (by either impregnation with the resins after paper-making orinclusion of the resins during paper-making). Examples of theresin-containing paper include interlaminar reinforced papers andresin-impregnated papers.

In addition to the above papers, as the substrate, there may be usedvarious other papers which are frequently employed in buildingapplications, such as linter papers, paper boards, base papers forgypsum boards and raw fabrics for vinyl-based wall papers which arecomposed of a paper and a vinyl chloride resin layer formed on a surfaceof the paper. Further, as the substrate, there may also be used suchpapers employed in business applications or for ordinary printing andpackaging purposes such as coated papers, art papers, parchment papers,glassine papers, paraffin papers and Japanese papers. Although beingdistinguished from these papers, as the substrate, there may also beused woven fabrics and nonwoven fabrics of various fibers which have anappearance and properties similar to those of papers. Examples ofvarious fibers include inorganic fibers such as glass fibers, asbestosfibers, potassium titanate fibers, alumina fibers, silica fibers andcarbon fibers, and synthetic resin fibers such as polyester fibers,acrylic fibers and vinylon fibers.

In the present invention, among these paper substrates, cellulose-basedsubstrates may be especially effectively used because cellulosemolecules of pulps contained therein tend to be oriented in the MDdirection (longitudinal direction) thereof. Such an MD orientation ofthe cellulose molecules causes considerable deterioration in foldingendurance of the substrate in the CD direction (lateral direction)thereof owing to irradiation of en electron beam thereto, so that theeffect of the present invention can be exhibited more remarkably whenapplied to the cellulose-based substrates.

The plastic film or the plastic sheet as the substrate may be made ofvarious synthetic resins. Examples of the synthetic resins includepolyethylene resins, polypropylene resins, polymethylpentene resins,polyvinyl chloride resins, polyvinylidene chloride resins, polyvinylalcohol resins, vinyl chloride/vinyl acetate copolymer resins,ethylene/vinyl acetate copolymer resins, ethylenevinyl alcohol copolymerresins, polyethylene terephthalate resins, polybutylene terephthalateresins, polyethylene naphthalate/isophthalate copolymer resins,polymethyl (meth)acrylate resins, polyethyl (meth)acrylate resins,polybutyl (meth)acrylate resins, polyamide resins such as typicallynylon 6 and nylon 66, cellulose triacetate resins, cellophane,polystyrene resins, polycarbonate resins, polyallylate resins andpolyimide resins.

Examples of the metal foil, metal sheet or metal plate include thosemade of aluminum, iron, stainless steel, copper, etc., as well as thoseplated with these metals. Examples of various wood plates includeveneer, plywood, laminated wood, particle board, and wood fiber platessuch as MDF (medium-density fiber board). Examples of the ceramicmaterials include ceramic building materials such as gypsum boards,calcium silicate boards and wood chip cement boards; pottery; glass;porcelain enamel; and baked tile. Examples of the other substrateinclude composites of various materials such as fiber-reinforced plastic(FRP) plates, laminates obtained by attaching an iron plate on bothsurfaces of a paper honeycomb, and laminates obtained by sandwiching apolyethylene resin sheet between two aluminum plates.

The thickness of the substrate 2 is not particularly limited. Thethickness of the plastic sheet substrate is usually about 20 to 150 μmand preferably 80 to 100 μm. The basic weight of the paper substrate isusually about 20 to 150 g/m² and preferably 30 to 100 g/m².

The colored layer 3 as shown in FIG. 1 which is formed so as to cover awhole surface of the substrate is provided for enhancing a designproperty of the decorative material according to the present invention,and may also be referred to as a concealing layer or a whole surfacesolid layer. Thus, the colored layer 3 serves for coloring the surfaceof the substrate 2 as intended. The colored layer usually has an opaquecolor in many cases, but may also show a tinted transparent color toutilize an original pattern of the underlying layer. In the case where awhite color of the substrate 2 is utilized or the substrate 2 itself issuitably tinted, it is not required to provide the colored layer 3.

The ink used for forming the colored layer may be those produced byappropriately mixing a binder with a colorant such as pigments and dyes,an extender pigment, a solvent, a stabilizer, a plasticizer, a catalystand a hardening agent. The binder is not particularly limited. Examplesof the binder include polyurethane-based resins, vinyl chloride/vinylacetate-based copolymer resins, vinyl chloride/vinyl acetate/acryliccompound-based copolymer resins, chlorinated polypropylene-based resins,acrylic resins, polyester-based resins, polyamide-based resins,butyral-based resins, polystyrene-based resins, nitrocellulose-basedresins and cellulose acetate-based resins. The binder may be optionallyselected from these resins, and these resins may be used alone or in theform of a mixture of any two or more thereof.

Examples of the colorant used in the colored layer include inorganicpigments such as carbon black (Japanese ink), iron black, titaniumwhite, antimony white, chrome yellow, titanium yellow, iron oxide red,cadmium red, ultramarine blue and cobalt blue; organic pigments and dyessuch as quinacridone red, isoindolinone yellow and phthalocyanine blue;metallic pigments made of scale-like foil pieces of aluminum, brass,etc., and nacreous (pearl) pigments made of scale-like foil pieces oftitanium dioxide-coated mica, basic lead carbonate, etc.

The thickness of the colored layer 3 is about 1 to 20 μm, and aso-called solid printing layer may be suitably used as the colored layer3.

The pattern layer 4 shown in FIG. 1 serves for imparting a decorativedesign to the substrate 2, and is formed by printing various patternswith an ink using a printer. Examples of the patterns formed by thepattern layer 4 include woodgrain patterns, stone-grain patternsimitating the surface of rocks such as marble pattern (e.g., travertinemarble pattern), cloth patterns imitating texture of cloth and fabric,tiling patterns, brick work patterns, and composite patterns thereofsuch as parquetry patterns and patchwork patterns. These patterns may beusually produced by multi-color printing with a process color includingyellow, red, blue and black colors, or by multi-color printing with aspecial color using printing plates corresponding to individual colorsof the pattern. The pattern ink used for forming the pattern layer 4 maybe the same as the ink used for forming the colored layer 3.

The penetration-preventing layer 5 shown in FIG. 1 may be optionallyprovided according to requirements, and has a function of inhibitingpenetration of an electron beam-curable resin for forming the surfaceprotective layer 6 into the substrate 2. In particular, the effect ofthe penetration-preventing layer 5 becomes more remarkable when thesubstrate 2 is made of a permeable material such as papers and nonwovenfabrics. Therefore, the penetration-preventing layer 5 may be formedbetween the substrate 2 and the surface protective layer 6, for example,between the substrate 2 and the colored layer 3, between the coloredlayer 3 and the pattern layer 4 or between the pattern layer 4 and thesurface protective layer 6 as shown in FIG. 1. As thepenetration-preventing layer 5, a uniform layer obtained by crosslinkingand curing a curable resin which exhibits a good adhesion to theelectron beam-curable resin forming the surface protective layer 6 isusually provided between the pattern layer 4 and the surface protectivelayer 6 as shown in FIG. 1, thereby not only allowing the surface of thecolored layer 3, the pattern layer 4, etc., if formed on the substrate2, to be smoothened, but also exhibiting the effect of enhancing abonding strength of these layers to the surface protective layer 6.

The surface protective layer 6 is formed by crosslinking and curing theelectron beam-curable resin composition as described above. The electronbeam-curable resin composition used herein means a resin compositioncapable of undergoing crosslinking and curing reactions upon irradiatingan electron beam thereto. More specifically, the electron beam-curableresin composition usable in the present invention may be appropriatelyselected from polymerizable monomers and polymerizable oligomers orprepolymers thereof which are conventionally used as an electronbeam-curable resin composition.

Typical examples of the suitable polymerizable monomers include(meth)acrylate monomers containing a radical-polymerizable unsaturatedgroup in a molecule thereof. Among these (meth)acrylate monomers,preferred are polyfunctional (meth)acrylates. Meanwhile, the term“(meth)acrylate” used herein means an acrylate, a methacrylate or boththereof. The polyfunctional (meth)acrylates are not particularly limitedas long as they have two or more ethylenically unsaturated bonds in amolecule thereof. Specific examples of the polyfunctional(meth)acrylates include ethylene glycol di(meth)acrylate, propyleneglycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycoldi(meth)acrylate, neopentyl glycol di(meth)acrylate hydroxypivalate,dicyclopentenyl di(meth)acrylate, caprolactone-modified dicyclopentenyldi(meth)acrylate, ethyleneoxide-modified phosphoric aciddi(meth)acrylate, allylated cyclohexyl di(meth)acrylate, isocyanuratedi(meth)acrylate, trimethylolpropane tri(meth)acrylate,ethyleneoxide-modified trimethylolpropane tri(meth)acrylate,dipentaerythritol tri(meth)acrylate, propionic acid-modifieddipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate,propyleneoxide-modified trimethylolpropane tri(meth)acrylate,tris(acryloxyethyl) isocyanurate, propionic acid-modifieddipentaerythritol penta(meth)acrylate, dipentaerythritolhexa(meth)acrylate, ethyleneoxide-modified dipentaerythritolhexa(meth)acrylate and caprolactone-modified dipentaerythritolhexa(meth)acrylate. These polyfunctional (meth)acrylates may be usedalone or in combination of any two or more thereof.

In the present invention, for the purpose of reducing a viscosity of thepolyfunctional (meth)acrylate, a monofunctional (meth)acrylate may beappropriately used in combination with the polyfunctional (meth)acrylateunless the effects of the present invention are adversely affected.Examples of the monofunctional (meth)acrylate include methyl(meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl(meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate,stearyl (meth)acrylate and isobornyl (meth)acrylate. Thesemonofunctional (meth)acrylates may be-used alone or in combination ofany two or more thereof.

As the polymerizable oligomer, there may be used oligomers having aradical-polymerizable unsaturated group in a molecule thereof. Examplesof the polymerizable oligomers include epoxy (meth)acrylate-basedoligomers, urethane (meth)acrylate-based oligomers, polyester(meth)acrylate-based oligomers and polyether (meth)acrylate-basedoligomers. The epoxy (meth)acrylate-based oligomers may be produced, forexample, by esterifying an oxirane ring of a relatively low-molecularweight bisphenol-type epoxy resin or novolak-type epoxy resin with(meth)acrylic acid. In addition, there may also be usedcarboxyl-modified epoxy (meth)acrylate oligomers obtained by partiallymodifying the above epoxy (meth)acrylate-based oligomers with a dibasiccarboxylic anhydride. The urethane (meth)acrylate-based oligomers may beproduced, for example, by esterifying a polyurethane oligomer obtainedby reacting a polyether polyol or a polyester polyol withpolyisocyanate, with (meth)acrylic acid. The polyester(meth)acrylate-based oligomers may be produced, for example, byesterifying a hydroxyl group of a polyester oligomer having hydroxylgroups at both terminal ends thereof which is obtained by condensationbetween a polycarboxylic acid and a polyhydric alcohol, with(meth)acrylic acid, or by esterifying a terminal hydroxyl group of anoligomer obtained by adding an alkyleneoxide to a polycarboxylic acid,with (meth)acrylic acid. The polyether (meth)acrylate-based oligomersmay be produced, for example, by esterifying a hydroxyl group of apolyether polyol with (meth)acrylic acid.

Examples of the other polymerizable oligomers include polybutadiene(meth)acrylate-based oligomers having a high hydrophobic property whichis in the form of a polybutadiene oligomer having a (meth)acrylate groupin a side chain thereof silicone (meth)acrylate-based oligomers having apolysiloxane bond in a main chain thereof aminoplast resin(meth)acrylate-based oligomers obtained by modifying an aminoplast resinhaving a large number of reactive groups in a small molecule thereof andoligomers having a cation-polymerizable functional group in a moleculethereof such as a novolak-type epoxy resin, a bisphenol-type epoxyresin, an aliphatic vinyl ether and an aromatic vinyl ether.

The electron beam-curable resin composition used in the presentinvention may also contain various additives according to requiredproperties of the obtained cured resin layer. Examples of the additivesinclude weather resistance-improving agents, abrasionresistance-improving agents, polymerization inhibitors, crosslinkingagents, infrared-absorbing agents, antistatic agents, adhesion-improvingagents, leveling agents, thixotropic agents, coupling agents,plasticizers, antifoaming agents, fillers, solvents and colorants.

As the weather resistance-improving agents, there may be usedultraviolet-absorbing agents or light stabilizers. The ultravioletabsorbing agents may be either inorganic or organic compounds. As thepreferred inorganic ultraviolet absorbing agents, there may be usedparticles of titanium dioxide, cerium oxide or zinc oxide which have anaverage particle size of about to 120 nm. As the organic ultravioletabsorbing agents, there may be used benzotriazole-based compounds.Specific examples of the benzotriazole-based compounds include2-(2-hydroxy-5-methylphenyl)benzotriazole,2-(2-hydroxy-3,5-di-tert-aminophenyl)benzotriazole and3-[3-(benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl]propionic ester ofpolyethylene glycol. Also, examples of the light stabilizer includehindered amine-based compounds. Specific examples of the lightstabilizer include bis(1,2,2,6,6-pentamethyl-4-piperizyl)2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2′-n-butyl malonate,bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate andtetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate.In addition, as the ultraviolet absorbing agent or the light stabilizer,there may also be used reactive ultraviolet absorbing agents or lightstabilizers having a polymerizable group such as a (meth)acryloyl groupin a molecule thereof.

Examples of the inorganic abrasion resistance-improving agent includegenerally-spherical particles of α-alumina, silica, kaolinite, ironoxide, diamond and silicon carbide. The shape of the inorganic abrasionresistance-improving agent may be a spherical shape, an ellipsoidalshape, a polyhedral shape or a scale-like shape. Among these shapes,preferred is the spherical shape although not particularly limitedthereto. Examples of the organic abrasion resistance-improving agentinclude beads of synthetic resins such as crosslinked acrylic resins andpolycarbonate resins. The particle size of the abrasionresistance-improving agent may be usually 30 to 200% of a thickness ofthe cure resin layer. Among these abrasion resistance-improving agents,spherical α-alumina particles are especially preferred because of highhardness, large effect of improving the abrasion resistance andrelatively easy production of the spherical particles.

Examples of the polymerization inhibitor include hydroquinone,p-benzoquinone, hydroquinone monomethyl ether, pyrogallol and t-butylcatechol. Examples of the crosslinking agent used in the presentinvention include polyisocyanate compounds, epoxy compounds, metalchelate compounds, aziridine compounds and oxazoline compounds.

Examples of the filler include barium sulfate, talc, clay, calciumcarbonate and aluminum hydroxide.

Examples of the colorant include known coloring pigments such asquinacridon red, isoindolinone yellow, phthalocyanine blue,phthalocyanine green, titanium oxide and carbon black.

Examples of the infrared-absorbing agent include dithiol-based metalcomplexes, phthalocyanine-based compounds and diimmonium compounds.

In the present invention, the above polymerizable monomers orpolymerizable oligomers as the electron beam-curable component andvarious additives are intimately mixed with each other at a given mixingratio to prepare a coating solution composed of the electronbeam-curable resin composition. The viscosity of the coating solution isnot particularly limited as long as the coating solution can be formedinto an cured resin layer on a surface of the substrate by thebelow-mentioned coating method.

In the present invention, the thus prepared coating solution is appliedonto a surface of the substrate in an amount capable of providing acured coating layer having a thickness of 1 to 20 μm, by known methodssuch as gravure coating, bar coating, roll coating, reverse roll coatingand Komma coating, preferably gravure coating, thereby forming anuncured resin layer thereon. The cured coating layer having a thicknessof 1 μm or larger can exhibit good functions as required. The thicknessof the cured surface protective layer is preferably about 2 to 20 μm.

In the present invention, the thus formed uncured resin layer isirradiated with an electron beam to cure the uncured resin layer. Theacceleration voltage for the electron beam may be appropriatelydetermined according to the kind of resin used and the thickness of theresin layer such that a rate of reduction in a folding endurance of theelectron beam-irradiated decorative material relative to a foldingendurance of the dry paper is 70% or lower. The higher accelerationvoltage leads to increase in penetrability of the electron beam.Therefore, when using a substrate which tends to be deteriorated byexposure to the electron beam, the acceleration voltage may becontrolled such that the depth of penetration of the electron beam issubstantially identical to the thickness of the resin layer, therebyinhibiting an excessive amount of the electron beam from beingirradiated to the substrate and minimizing deterioration of thesubstrate owing to irradiation with an excessive amount of the electronbeam. In order to control the rate of reduction in folding endurance ofthe electron beam-irradiated decorative material to 70% or lower, theacceleration voltage applied to the electron beam is preferably as lowas possible. More specifically, the acceleration voltage is preferably30 to 150 kV and more preferably 70 to 130 kV. When the accelerationvoltage is 30 kV or higher, a mechanical stability of the electronbeam-irradiating apparatus can be ensured, whereas when the accelerationvoltage is 150 kV or lower, the substrate can be inhibited from beingdeteriorated, thereby achieving the aimed effects of the presentinvention. Further, in view of preventing the deterioration of thesubstrate, the acceleration voltage is preferably controlled to 110 kVor lower, more preferably 90 kV or lower and still more preferably 70 kVor lower.

On the other hand, in view of not only preventing the deterioration ofthe substrate but also allowing the electron beam-curable resincomposition to be sufficiently crosslinked and cured even under arelatively low acceleration voltage, the acceleration voltage ispreferably controlled to 90 to 110 kV.

The exposure dose of the electron beam is preferably such an amountcapable of saturating a crosslinking density of the resin layer, and maybe selected from the range of usually 5 to 300 kGy, preferably 10 to 100kGy and more preferably 30 to 70 kGy. In the present invention, sincethe acceleration voltage can be lowered, the substrate can be inhibitedfrom being deteriorated. For this reason, the exposure dose of theelectron beam can be increased. As a result, the crosslinking density ofthe resin layer forming the surface protective layer can be increased toa higher level than ordinarily, resulting in especially good surfaceproperties of the resultant decorative material.

As described above, in the present invention, by suitably controllingthe acceleration voltage and the exposure dose, it is possible to notonly inhibit the deterioration of the substrate but also increase thecrosslinking density of the surface protective layer. In view of a goodbalance between prevention of deterioration of the substrate and thehigh crosslinking density of the surface protective layer, theacceleration voltage is preferably in the range of 90 to 110 kV, and theexposure dose is preferably in the range of 50 to 70 kGy.

The electron beam source is not particularly limited, and examples ofthe electron beam source usable in the present invention include variouselectron beam accelerators such as Cockroft-Walton type, van de Graafftype, resonance transformer type, insulating core transformer type,linear type, Dynamitron type and high-frequency type.

The thus formed cured resin layer may also contain various additives toimpart various functions or performances thereto. Examples of thevarious functions imparted by addition of the additives include thosecapable of attaining a high hardness and a good marring resistance suchas functions of so-called hard coat, anti-fogging coat, anti-foulingcoat, anti-glare coat, anti-reflecting coat, ultraviolet-shielding coatand infrared-shielding coat.

The decorative material of the present invention can be used as adecorative plate by attaching to various substrates. The substrate as anadherend is not particularly limited, and may be appropriately selectedfrom plastic sheets, metal plates, wood plates such as timber, andceramic materials according to the applications. One or both surfaces ofthese substrates, in particular, plastic sheet substrates, may beoptionally subjected to various physical and chemical surface treatmentssuch as those treatments using oxidation method and convex/concaveforming method in order to enhance adhesion of the substrate to thedecorative material.

Examples of the treatments using the oxidation method include coronadischarge treatment, chromate treatment, flame treatment, hot airtreatment and ozone/ultraviolet treatment. Examples of theconvex/concave forming method include a sandblast method and asolvent-treating method. The surface treatment to be conducted may beappropriately selected according to the kind of substrate used, and ingeneral, the corona discharge treatment is preferably used because ofgood effects and facilitated operation thereof.

The plastic sheets may be made of various synthetic resins. Examples ofthe synthetic resins include polyethylene resins, polypropylene resins,polymethylpentene resins, polyvinyl chloride resins, polyvinylidenechloride resins, polyvinyl alcohol resins, vinyl chloride/vinyl acetatecopolymer resins, ethylene/vinyl acetate copolymer resins,ethylene/vinyl alcohol copolymer resins, polyethylene terephthalateresins, polybutylene terephthalate resins, polyethylenenaphthalate/isophthalate copolymer resins, polymethyl methacrylateresins, polyethyl methacrylate resins, polybutyl acrylate resins,polyamide resins such as typically nylon 6 and nylon 66, cellulosetriacetate resins, cellophane, polystyrene resins, polycarbonate resins,polyallylate resins and polyimide resins.

Examples of the metal plates include those plates made of aluminum,iron, stainless steel, copper, etc. In addition, there may also be usedthose substrates which are plated with these metals.

Examples of the wood plates include sliced veneers, veneers, plywood,particle boards and medium-density fiber (MDF) boards which are made ofvarious materials such as Japanese cryptmeria, hinoki cypress, keyaki,pine, lauan, teak and Melapi. These wood plates may be used alone or inthe form of a laminate of any two or more thereof. Meanwhile, the woodplates used herein involve not only plates made of wooden materials, butalso plastic plates containing paper powder and reinforced high-strengthpapers.

Examples of the ceramic materials include ceramic-based buildingmaterials such as gypsum boards, calcium silicate boards and wood chipcement boards, pottery, glass, porcelain enamels, baked tiles and boardsmade of volcanic ash as a main raw material.

In addition to the above illustrated substrates, there may also be usedcomposite plates of various materials such as a fiber-reinforced plastic(FRP) plate, a plate produced by attaching an iron plate onto bothsurfaces of a paper honeycomb and a polyethylene resin sheet sandwichedbetween two aluminum plates.

The substrate may be subjected to further treatments for forming aprimer layer thereon, adjusting a hue thereof by painting, or previouslyproviding a designed pattern thereon in view of a good design propertythereof. The substrate as an adherend may be a plate material such as aflat plate or a curved plate made of various materials, or athree-dimensional product (molded article) in which the materials areused singly or in the form of a composite thereof.

The substrate may be attached with a backing or lining material such asJapanese papers, machine-made papers, synthetic papers, nonwovenfabrics, woven fabrics, cheese cloths, impregnated papers and syntheticresin sheets. By using such a substrate to which the backing or liningmaterial is attached, the decorative material can be reinforced byitself, and can be effectively prevented from suffering from occurrenceof cracks or rupture and bleeding of adhesives onto a surface thereofresulting in reduction of defectives and facilitated handling procedureas well as increased yield.

The substrate on which the decorative material in the form of a cutsheet or a continuous sheet is placed through an adhesive is thenpressed or compressed using a laminating apparatus such as a cold press,a hot press, a roll press, a laminator, a wrapping machine, aedge-bonding machine and a vacuum press to allow the decorative materialto adhere to a surface of the substrate, thereby producing a decorativeplate.

The adhesive may be applied using a coating apparatus such as a spraycoater, a spreader and a bar coater. Examples of the adhesive includevinyl acetate resin-based adhesives, urea resin-based adhesives,melamine resin-based adhesives, phenol resin-based adhesives andisocyanate-based adhesives. These adhesives may be used alone or in theform of a mixed adhesive obtained by mixing any two or more thereof witheach other at an optional mixing ratio. The adhesive may contain, ifrequired, inorganic powder such as talc, calcium carbonate, clay andtitanium white, wheat flour, wood chips, plastic chips, colorants,insecticides, mildew-proof agents, etc. In general, the adhesive has asolid content of 35 to 80% by mass, and is applied onto the surface ofthe substrate in an amount of 50 to 300 g/m².

The decorative material may be usually attached onto the substrate byforming an adhesive layer on a back surface of the decorative materialof the present invention and then bonding the substrate onto theadhesive layer, or by applying an adhesive onto the substrate and thenbonding the decorative material onto the substrate through the adhesive.

The thus produced decorative plate may be cut into an optional size, andthen the surface or butt end portion thereof may be subjected tooptional decorating processes such as grooving and chamfering by meansof a cutting machine such as a router and a cutter. The resultantdecorative plate may be used in various applications, e.g., interior orexterior materials for buildings such as walls, ceilings and floors;surface decorative plates for fittings such as window frames, doors,balustrades, baseboards, verandahs and malls as well as surfacedecorative plates for kitchen wares, furniture, light-electricalappliances or OA devices, interior and exterior equipments for vehicles,etc.

EXAMPLES

The present invention will be described in more detail by referring tothe following examples. However, it should be noted that these examplesare only illustrative and not intended to limit the invention thereto.

(Evaluation Methods) (1) Folding Endurance

The folding endurance of the decorative material was evaluated asfollows. That is, a test specimen of the decorative material wassubjected to folding endurance test according to TAPPI T511 (FoldingEndurance of Papers (MIT testing machine)) to measure the number offolding reciprocating motions required until reaching breakage of thetest specimen of the decorative material which was determined as afolding endurance of the decorative material. The folding endurance ofthe decorative material was measured in both the MD direction(longitudinal direction) and the CD direction (lateral direction) of thesubstrate.

(2) Tensile Strength and Tensile Elongation

According to JIS K-7161, a test specimen of the decorative material waspulled at a constant speed of 20 mm/s using a tension/compression testeravailable from A & D Co., Ltd., to measure a maximum load (i.e., atensile strength (kgf)) applied until reaching breakage of the testspecimen, and an elongation (i.e., a tensile elongation (%)) requireduntil reaching breakage of the test specimen.

(3) Stain Resistance

According to JIS K-6902, contaminants were applied onto a surface of thedecorative material, and then wiped off. The surface of the decorativematerial was observed by naked eyes to determine the extent of anyresidual contaminants remaining thereon. The results were evaluatedaccording to the following criteria:

-   -   ⊚: No contaminants remained    -   Δ: Slight amount of contaminants remained, but within        practically acceptable level    -   x: Considerable amount of contaminants remained

(4) Abrasion Resistance

The decorative material was subjected to JAS Abrasion C Test or JASAbrasion A Test. The surface of the decorative material after beingsubjected to a specific number of the tests was observed to determine aresidual percentage of patterns thereon.

(5) Marring Resistance

Steel wool (#0000) was fitted to a weight adjusted to a load of 29.4 kPa(300 g/cm²), and the surface of the decorative material was rubbed withthe steel wool 5 times. The rubbed surface portion of the decorativematerial was observed by naked eyes to determine the change in gloss,and the results were evaluated according to the following criteria:

-   -   ⊚: No change in gloss occurred    -   Δ: Slight change in gloss occurred, but within practically        acceptable level    -   x: Severe change in gloss occurred

(6) Releasability of Cellophane Tape

A cellophane tape (cellophane adhesive tape “CELLOTAPE” (trademark)available from Nichiban Co., Ltd.; width: 2.5 mm) was attached onto asurface of the decorative material, and then forcibly peeled off. Thereleasability was evaluated by a load required for peeling off thecellophane tape from the decorative material. Meanwhile, the smallerpeel strength means more preferred results.

Example 1

Using an ordinary paper for building materials having a basis weight of30 g/m² as the substrate 2, a whole solid printing layer having acoating amount of 17 g/m² was formed on one surface of the substratewith an urethane-based ink containing nitrocellulose as a binder by agravure printing method, thereby forming a colored layer 3. Then, apenetration-preventing layer 5 (primer layer) was formed on the coloredlayer 3 using an acrylic ink.

Next, an electron beam-curable resin composition composed of 60 parts bymass of ethyleneoxide-modified trimethylolpropane ethyleneoxidetriacrylate as a trifunctional acrylate monomer, 40 parts by mass ofdipentaerythritol hexaacrylate as a hexafunctional acrylate monomer, 2parts by mass of silica particles having an average particle size of 5μm and 1 part by mass of a silicone acrylate prepolymer was applied in acoating amount of 5 g/m² on the penetration-preventing layer 5 (primerlayer) by a gravure offset coater method. After coating, an electronbeam was irradiated to the thus applied electron beam-curable resincomposition at an acceleration voltage of 110 kV and an exposure dose of30 kGy (3 Mrad) to cure the composition, thereby forming a surfaceprotective layer 6. Then, the resultant laminate was cured at 70° C. for24 h, thereby obtaining a decorative material. The thus obtaineddecorative material was examined to evaluate the above properties. Theresults are shown in Table 1.

Example 2

The same procedure as in Example 1 was repeated except that the exposuredose of the electron beam irradiated was changed to 50 kGy (5 Mrad),thereby obtaining a decorative material. The thus obtained decorativematerial was examined to evaluate the above properties. The results areshown in Table 1.

Comparative Example 1

The same procedure as in Example 1 was repeated except that theacceleration voltage for the electron beam irradiated was changed to 175kV, thereby obtaining a decorative material. The thus obtaineddecorative material was examined to evaluate the above properties. Theresults are shown in Table 1.

Example 3

Using an interlaminar-reinforced paper for building materials having abasis weight of 60 g/m² as the substrate 2, a (whole surface solid)layer having a coating amount of 6 g/m² was formed on one surface of thesubstrate with a nitrocellulose-based ink containing an acrylic resin asa binder by a gravure printing method, thereby forming a colored layer3. Using an alkyd-based ink containing nitrocellulose as a binder,gravure printing was conducted to form a pattern layer 4 with awoodgrain pattern on the colored layer 3. Then, a butyral/urethane-basedink was gravure-printed in a coating amount of 1 g/m² over a wholesurface of the underlying layers to form a penetration-preventing layer5 (primer layer).

Next, an electron beam-curable resin composition composed of 60 parts bymass of ethyleneoxide-modified trimethylolpropane ethyleneoxidetriacrylate as a trifunctional acrylate monomer, 40 parts by mass ofdipentaerythritol hexaacrylate as a hexafunctional acrylate monomer, 2parts by mass of silica particles having an average particle size of 6μm and 1 part by mass of a silicone acrylate prepolymer was applied in acoating amount of 13 g/m² on the penetration-preventing layer 5 by agravure offset coater method. After coating, an electron beam wasirradiated to the thus applied electron beam-curable resin compositionat an acceleration voltage of 110 kV and an exposure dose of 30 kGy (3Mrad) to cure the composition, thereby forming a surface protectivelayer 6. Then, the resultant laminate was cured at 70° C. for 24 h,thereby obtaining a decorative material. The thus obtained decorativematerial was examined to evaluate the above properties. The results areshown in Table 1.

Example 4

The same procedure as in Example 3 was repeated except that the exposuredose of the electron beam irradiated was changed to 50 kGy (6 Mrad),thereby obtaining a decorative material. The thus obtained decorativematerial was examined to evaluate the above properties. The results areshown in Table 1.

Comparative Example 2

The same procedure as in Example 1 was repeated except that theacceleration voltage for the electron beam irradiated was changed to 175kV, thereby obtaining a decorative material. The thus obtaineddecorative material was examined to evaluate the above properties. Theresults are shown in Table 1.

TABLE 1-1 Example 1 Example 2 Com. Ex. 1 Acceleration voltage (kV) 110110 175 Exposure dose (kGy) 30 50 30 Folding MD Dry paper 561 561 561endurance direction Electron beam-irradiated 491 207 156 decorativematerial Reduction rate (%) 12 67 72 CD Dry paper 338 338 338 directionElectron beam-irradiated 165 146 58 decorative material Reduction rate(%) 51 57 83 Tensile MD Dry paper 4.8 4.8 4.8 strength directionElectron beam-irradiated 4.7 4.1 4.8 (kgf) decorative material CD Drypaper 3.7 3.7 3.7 direction Electron beam-irradiated 3.9 3.9 3.7decorative material Tensile MD Dry paper 3.6 3.6 3.6 elongationdirection Electron beam-irradiated 3.9 3.1 3.4 (%) decorative materialCD Dry paper 4.1 4.1 4.1 direction Electron beam-irradiated 4.0 3.3 3.7decorative material Stain resistance ◯ ⊚ ◯ Abrasion resistance JAS Cabrasion test 100 100 100 JAS A abrasion test — — — Marring resistance ⊚⊚ ⊚ Releasability of cellophane tape (gf) 37 40 39

TABLE 1-2 Example 3 Example 4 Com. Ex. 2 Acceleration voltage (kV) 110110 175 Exposure dose (kGy) 30 50 30 Folding MD Dry paper 1007 1007 1007endurance direction Electron beam-irradiated 550 260 213 decorativematerial Reduction rate (%) 45 74 79 CD Dry paper 1791 1791 1791direction Electron beam-irradiated 1101 765 447 decorative materialReduction rate (%) 39 57 75 Tensile MD Dry paper 4.8 4.8 4.8 strengthdirection Electron beam-irradiated 7.9 6.7 7.0 (kgf) decorative materialCD Dry paper 3.6 3.6 3.6 direction Electron beam-irradiated 5.9 5.4 5.3decorative material Tensile MD Dry paper 3.6 3.6 3.6 elongationdirection Electron beam-irradiated 4.6 3.7 3.5 (%) decorative materialCD Dry paper 8.2 8.2 8.2 direction Electron beam-irradiated 12.7 10.410.4 decorative material Stain resistance ◯ ◯ ◯ Abrasion resistance JASC abrasion test — — — JAS A abrasion test 30 30 30 Marring resistance ◯◯ ◯ Releasability of cellophane tape (gf) 43 43 46

Reference Example 1

A particle board as a substrate having a thickness of 9 mm was bondedonto a back surface of the decorative material obtained in Example 1through an adhesive layer formed by applying onto the particle board, anurea-based synthetic resin adhesive “OHSHIKA RESIN” available fromOhhika Co., Ltd., in a coating amount of 60 g/m² (wet), therebyproducing a wooden decorative plate.

INDUSTRIAL APPLICABILITY

In accordance with the present invention, there can be obtained adecorative material which hardly undergoes deterioration of a substrateeven upon irradiation with an electron beam and is excellent in surfaceproperties such as stain resistance and abrasion resistance. Thedecorative material is suitably used in various applications includinginterior materials for buildings such as walls, surface materials forfittings such as doors, or furniture, etc.

What is claimed is:
 1. A process for producing a decorative materialcomprising a substrate, and a pattern layer and/or a colored layer, anda surface protective layer which are successively laminated on thesubstrate, wherein the surface protective layer is obtained bycrosslinking and curing an electron beam-curable resin composition at anacceleration voltage of 30 to 150 kV and an exposure doss of 30 to 70kGy.